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<p style="padding-top: 0pt; " class="paragraph_style_7">Chapter 18: wolfCrypt API Reference<br/></p>
<p class="paragraph_style_7"><br/></p>
<p class="paragraph_style_8">18.13  DSA<br/></p>
<p class="paragraph_style_8"><br/></p>
<p class="paragraph_style_9">The functions in this section expose DSA functionality to calling applications.<span class="style_2"><br/></span></p>
<p class="paragraph_style_10"><br/></p>
<p class="paragraph_style_10"><br/></p>
<div class="paragraph paragraph_style_10"><div style="height: 1px; width: 693px;  height: 1px; left: 0px; position: relative; top: 1px; width: 693px; " class="tinyText inline-block"><div style="position: relative; width: 693px; "><img src="Docs-wolfssl-manual-18-13-wolfcrypt-api-dsa_files/shapeimage_11.jpg" alt="" style="height: 1px; left: 0px; position: absolute; top: 0px; width: 693px; "/></div></div><br/></div>
<p class="paragraph_style_10"><br/></p>
<p class="paragraph_style_11"><br/></p>
<p class="paragraph_style_12">wc_InitDsaKey<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Synopsis:<br/></p>
<p class="paragraph_style_9">#include &lt;wolfssl/wolfcrypt/dsa.h&gt;<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_9">void wc_InitDsaKey(DsaKey* key);<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Description:<br/></p>
<p class="paragraph_style_9">This function initializes a DsaKey object in order to use it for authentication via the Digital Signature Algorithm (DSA). <br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Return Values:<br/></p>
<p class="paragraph_style_9">No return value for this function.<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Parameters:<br/></p>
<p class="paragraph_style_9"><span class="style_3">key</span> - pointer to the DsaKey structure to initialize<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Example:<br/></p>
<p class="paragraph_style_14">DsaKey key;<br/></p>
<p class="paragraph_style_14">wc_InitDsaKey(&amp;key); // initialize DSA key<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">See Also:<br/></p>
<p class="paragraph_style_9">wc_FreeDsaKey<br/></p>
<p class="paragraph_style_9"><br/></p>
<div class="paragraph paragraph_style_9"><div style="height: 1px; width: 693px;  height: 1px; left: 0px; position: relative; top: 1px; width: 693px; " class="tinyText inline-block"><div style="position: relative; width: 693px; "><img src="Docs-wolfssl-manual-18-13-wolfcrypt-api-dsa_files/shapeimage_12.jpg" alt="" style="height: 1px; left: 0px; position: absolute; top: 0px; width: 693px; "/></div></div><br/></div>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_12"><br/></p>
<p class="paragraph_style_12">wc_FreeDsaKey<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Synopsis:<br/></p>
<p class="paragraph_style_9">#include &lt;wolfssl/wolfcrypt/dsa.h&gt;<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_9">void wc_FreeDsaKey(DsaKey* key);<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Description:<br/></p>
<p class="paragraph_style_9">This function frees a DsaKey object after it has been used.<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Return Values:<br/></p>
<p class="paragraph_style_9">No return value for this function.<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Parameters:<br/></p>
<p class="paragraph_style_9"><span class="style_3">key</span> - pointer to the DsaKey structure to free<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Example:<br/></p>
<p class="paragraph_style_14">DsaKey key;<br/></p>
<p class="paragraph_style_14">// initialize key, use for authentication<br/></p>
<p class="paragraph_style_14">...<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">wc_FreeDsaKey(&amp;key); // free DSA key<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">See Also:<br/></p>
<p class="paragraph_style_9">wc_FreeDsaKey<br/></p>
<p class="paragraph_style_9"><br/></p>
<div class="paragraph paragraph_style_9"><div style="height: 1px; width: 693px;  height: 1px; left: 0px; position: relative; top: 1px; width: 693px; " class="tinyText inline-block"><div style="position: relative; width: 693px; "><img src="Docs-wolfssl-manual-18-13-wolfcrypt-api-dsa_files/shapeimage_13.jpg" alt="" style="height: 1px; left: 0px; position: absolute; top: 0px; width: 693px; "/></div></div><br/></div>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_12"><br/></p>
<p class="paragraph_style_12">wc_DsaSign<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Synopsis:<br/></p>
<p class="paragraph_style_9">#include &lt;wolfssl/wolfcrypt/dsa.h&gt;<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_9">int wc_DsaSign(const byte* digest, byte* out, DsaKey* key, RNG* rng);<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Description:<br/></p>
<p class="paragraph_style_9">This function signs the input digest and stores the result in the output buffer, out. <br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Return Values:<br/></p>
<p class="paragraph_style_9"><span class="style_3">0</span>: Returned on successfully signing the input digest<br/></p>
<p class="paragraph_style_9"><span class="style_3">MP_INIT_E</span>, <span class="style_3">MP_READ_E</span>, <span class="style_3">MP_CMP_E</span>, <span class="style_3">MP_INVMOD_E</span>, <span class="style_3">MP_EXPTMOD_E</span>, <span class="style_3">MP_MOD_E</span>, <span class="style_3">MP_MUL_E</span>, <span class="style_3">MP_ADD_E</span>, <span class="style_3">MP_MULMOD_E</span>, <span class="style_3">MP_TO_E</span>, and <span class="style_3">MP_MEM</span> may be returned if there is an error in processing the DSA signature.<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Parameters:<br/></p>
<p class="paragraph_style_9"><span class="style_3">digest</span> - pointer to the hash to sign<br/></p>
<p class="paragraph_style_9"><span class="style_3">out</span> - pointer to the buffer in which to store the signature<br/></p>
<p class="paragraph_style_9"><span class="style_3">key</span> - pointer to the initialized DsaKey structure with which to generate the signature<br/></p>
<p class="paragraph_style_9"><span class="style_3">rng</span> - pointer to an initialized RNG to use with the signature generation<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Example:<br/></p>
<p class="paragraph_style_14">DsaKey key;<br/></p>
<p class="paragraph_style_14">// initialize DSA key, load private Key<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">int ret;<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">RNG rng;<br/></p>
<p class="paragraph_style_14">wc_InitRng(&amp;rng);<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">byte hash[] = { /* initialize with hash digest */ };<br/></p>
<p class="paragraph_style_14">byte signature[40]; // signature will be 40 bytes (320 bits)<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">ret = wc_DsaSign(hash, signature, &amp;key, &amp;rng);<br/></p>
<p class="paragraph_style_14">if (ret != 0) { <br/></p>
<p class="paragraph_style_14">// error generating DSA signature<br/></p>
<p class="paragraph_style_14">}<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">See Also:<br/></p>
<p class="paragraph_style_9">wc_DsaVerify<br/></p>
<p class="paragraph_style_9"><br/></p>
<div class="paragraph paragraph_style_9"><div style="height: 1px; width: 693px;  height: 1px; left: 0px; position: relative; top: 1px; width: 693px; " class="tinyText inline-block"><div style="position: relative; width: 693px; "><img src="Docs-wolfssl-manual-18-13-wolfcrypt-api-dsa_files/shapeimage_14.jpg" alt="" style="height: 1px; left: 0px; position: absolute; top: 0px; width: 693px; "/></div></div><br/></div>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_12"><br/></p>
<p class="paragraph_style_12">wc_DsaVerify<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Synopsis:<br/></p>
<p class="paragraph_style_9">#include &lt;wolfssl/wolfcrypt/dsa.h&gt;<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_9">int wc_DsaVerify(const byte* digest, const byte* sig, DsaKey* key, int* answer);<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Description:<br/></p>
<p class="paragraph_style_9">This function verifies the signature of a digest, given a private key. It stores whether the key properly verifies in the answer parameter, with 1 corresponding to a successful verification, and 0 corresponding to failed verification. <br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Return Values:<br/></p>
<p class="paragraph_style_9"><span class="style_3">0</span>: Returned on successfully processing the verify request. Note: this does not mean that the signature is verified, only that the function succeeded<br/></p>
<p class="paragraph_style_9"><span class="style_3">MP_INIT_E</span>, <span class="style_3">MP_READ_E</span>, <span class="style_3">MP_CMP_E</span>, <span class="style_3">MP_INVMOD_E</span>, <span class="style_3">MP_EXPTMOD_E</span>, <span class="style_3">MP_MOD_E</span>, <span class="style_3">MP_MUL_E</span>, <span class="style_3">MP_ADD_E</span>, <span class="style_3">MP_MULMOD_E</span>, <span class="style_3">MP_TO_E</span>, and <span class="style_3">MP_MEM</span> may be returned if there is an error in verifying the DSA signature<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Parameters:<br/></p>
<p class="paragraph_style_9"><span class="style_3">digest</span> - pointer to the digest containing the subject of the signature<br/></p>
<p class="paragraph_style_9"><span class="style_3">sig</span> - pointer to the buffer containing the signature to verify<br/></p>
<p class="paragraph_style_9"><span class="style_3">key</span> - pointer to the initialized DsaKey structure with which to verify the signature<br/></p>
<p class="paragraph_style_9"><span class="style_3">answer</span> - pointer to an integer which will store whether the verification was successful<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Example:<br/></p>
<p class="paragraph_style_14">DsaKey key;<br/></p>
<p class="paragraph_style_14">// initialize DSA key, load public Key<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">int ret;<br/></p>
<p class="paragraph_style_14">int verified;<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">byte hash[] = { /* initialize with hash digest */ };<br/></p>
<p class="paragraph_style_14">byte signature[] = { /* initialize with signature to verify */ };<br/></p>
<p class="paragraph_style_14">ret = wc_DsaVerify(hash, signature, &amp;key, &amp;verified);<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">if (ret != 0) { <br/></p>
<p class="paragraph_style_14">// error processing verify request<br/></p>
<p class="paragraph_style_14">} else if (answer == 0) {<br/></p>
<p class="paragraph_style_14">// invalid signature<br/></p>
<p class="paragraph_style_14">}<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">See Also:<br/></p>
<p class="paragraph_style_9">wc_DsaSign<br/></p>
<p class="paragraph_style_9"><br/></p>
<div class="paragraph paragraph_style_9"><div style="height: 1px; width: 693px;  height: 1px; left: 0px; position: relative; top: 1px; width: 693px; " class="tinyText inline-block"><div style="position: relative; width: 693px; "><img src="Docs-wolfssl-manual-18-13-wolfcrypt-api-dsa_files/shapeimage_15.jpg" alt="" style="height: 1px; left: 0px; position: absolute; top: 0px; width: 693px; "/></div></div><br/></div>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_12"><br/></p>
<p class="paragraph_style_12">wc_DsaPublicKeyDecode<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Synopsis:<br/></p>
<p class="paragraph_style_9">#include &lt;wolfssl/wolfcrypt/dsa.h&gt;<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_9">int wc_DsaPublicKeyDecode(const byte* input, word32* inOutIdx, DsaKey* key,<br/></p>
<p class="paragraph_style_9">word32 inSz);<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Description:<br/></p>
<p class="paragraph_style_9">This function decodes a DER formatted certificate buffer containing a DSA public key, and stores the key in the given DsaKey structure. It also sets the inOutIdx parameter according to the length of the input read.<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Return Values:<br/></p>
<p class="paragraph_style_9"><span class="style_3">0</span>: Returned on successfully setting the public key for the DsaKey object<br/></p>
<p class="paragraph_style_9"><span class="style_3">ASN_PARSE_E</span>: Returned if there is an error in the encoding while reading the certificate buffer<br/></p>
<p class="paragraph_style_9"><span class="style_3">ASN_DH_KEY_E</span>: Returned if one of the DSA parameters is incorrectly formatted<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Parameters:<br/></p>
<p class="paragraph_style_9"><span class="style_3">input</span> - pointer to the buffer containing the DER formatted DSA public key<br/></p>
<p class="paragraph_style_9"><span class="style_3">inOutIdx</span> - pointer to an integer in which to store the final index of the certificate read<br/></p>
<p class="paragraph_style_9"><span class="style_3">key</span> - pointer to the DsaKey structure in which to store the public key<br/></p>
<p class="paragraph_style_9"><span class="style_3">inSz</span> - size of the input buffer<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Example:<br/></p>
<p class="paragraph_style_9">i<span class="style_4">nt ret, idx=0;<br/></span></p>
<p class="paragraph_style_9"><span class="style_4"><br/></span></p>
<p class="paragraph_style_9"><span class="style_4">DsaKey key;<br/></span></p>
<p class="paragraph_style_9"><span class="style_4">wc_InitDsaKey(&amp;key);<br/></span></p>
<p class="paragraph_style_9"><span class="style_4"><br/></span></p>
<p class="paragraph_style_9"><span class="style_4">byte derBuff[] = { /* DSA public key */ };<br/></span></p>
<p class="paragraph_style_9"><span class="style_4"><br/></span></p>
<p class="paragraph_style_9"><span class="style_4">ret = wc_DsaPublicKeyDecode(derBuff, &amp;idx, &amp;key, inSz);<br/></span></p>
<p class="paragraph_style_9"><span class="style_4">if (ret != 0) { <br/></span></p>
<p class="paragraph_style_9"><span class="style_4">// error reading public key<br/></span></p>
<p class="paragraph_style_9"><span class="style_4">}</span><br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">See Also:<br/></p>
<p class="paragraph_style_9">wc_InitDsaKey, wc_DsaPrivateKeyDecode<br/></p>
<p class="paragraph_style_9"><br/></p>
<div class="paragraph paragraph_style_9"><div style="height: 1px; width: 693px;  height: 1px; left: 0px; position: relative; top: 1px; width: 693px; " class="tinyText inline-block"><div style="position: relative; width: 693px; "><img src="Docs-wolfssl-manual-18-13-wolfcrypt-api-dsa_files/shapeimage_16.jpg" alt="" style="height: 1px; left: 0px; position: absolute; top: 0px; width: 693px; "/></div></div><br/></div>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_12"><br/></p>
<p class="paragraph_style_12">wc_DsaPrivateKeyDecode<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Synopsis:<br/></p>
<p class="paragraph_style_9">#include &lt;wolfssl/wolfcrypt/dsa.h&gt;<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_9">int wc_DsaPrivateKeyDecode(const byte* input, word32* inOutIdx, DsaKey* key,<br/></p>
<p class="paragraph_style_9">word32 inSz)<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Description:<br/></p>
<p class="paragraph_style_9">This function decodes a DER formatted certificate buffer containing a DSA private key, and stores the key in the given DsaKey structure. It also sets the inOutIdx parameter according to the length of the input read.<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Return Values:<br/></p>
<p class="paragraph_style_9"><span class="style_3">0</span>: Returned on successfully setting the private key for the DsaKey object<br/></p>
<p class="paragraph_style_9"><span class="style_3">ASN_PARSE_E</span>: Returned if there is an error in the encoding while reading the certificate buffer<br/></p>
<p class="paragraph_style_9"><span class="style_3">ASN_DH_KEY_E</span>: Returned if one of the DSA parameters is incorrectly formatted<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Parameters:<br/></p>
<p class="paragraph_style_9"><span class="style_3">input</span> - pointer to the buffer containing the DER formatted DSA private key<br/></p>
<p class="paragraph_style_9"><span class="style_3">inOutIdx</span> - pointer to an integer in which to store the final index of the certificate read<br/></p>
<p class="paragraph_style_9"><span class="style_3">key</span> - pointer to the DsaKey structure in which to store the private key<br/></p>
<p class="paragraph_style_9"><span class="style_3">inSz</span> - size of the input buffer<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">Example:<br/></p>
<p class="paragraph_style_14">int ret, idx=0;<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">DsaKey key;<br/></p>
<p class="paragraph_style_14">wc_InitDsaKey(&amp;key);<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">byte derBuff[] = { /* DSA private key */ };<br/></p>
<p class="paragraph_style_14"><br/></p>
<p class="paragraph_style_14">ret = wc_DsaPrivateKeyDecode(derBuff, &amp;idx, &amp;key, inSz);<br/></p>
<p class="paragraph_style_14">if (ret != 0) { <br/></p>
<p class="paragraph_style_14">// error reading private key<br/></p>
<p class="paragraph_style_14">}<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_13">See Also:<br/></p>
<p class="paragraph_style_9">wc_InitDsaKey, wc_DsaPublicKeyDecode<br/></p>
<p class="paragraph_style_9"><br/></p>
<p class="paragraph_style_10"><br/></p>
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